Directed, heritable alterations in gene expression, called epigenetic changes, have been proposed as a basic mechanism for tumor transformation. The major objectives of this project are: to find out to what extent epigenetic changes in the production of specific growth factors can account for autonomous growth, tumor progression, and tumor reversal in plants. The specific aims for the current grant period are: 1) to study the molecular basis for heritable changes in the cell division factor autotrophy of cultured tobacco cells: 2) to identify relationships between the nature of the association of Ti plasmid DNA sequences with the tumor cell and expression of autonomous growth; and 3) to use Vinca lines in culture to test the hypothesis that tumor progression involves a perturbation of cells followed by selection for more autonomous cell types.